Class 12 Computer Science Chapter 3 Notes

• Define Feasibility Study, Requirements Analysis, Project Planning and Data Analysis: Feasibility Study : This is also called preliminary investigation of the required database. It involves the area identification and selection i.e. which area or aspect is to be selected to start with. After the project is selected, it is allocated a specific find and a proper planning is chalked out for its practical implementation. Side by side, a proper market analysis is also worked out.
• Describe Ingredients of Data Modeling.
• Describe Entities / Objects, Attributes , Relationships, Cardinality, Modality and ERD (Entity Relationship Diagram).
• Describe major objective of Database Design.
  
• Explain Database Development process with diagram.
• Explain Conceptual (Logical) Database Design.
• Explain Physical Database Design:  To implement the database as a set of stored records, files, indexes and other data structures that will provide adequate performance and ensure database integrity, security and recoverability]. There are three major inputs to Physical database design : Logical Database Structures : Developed during logical database design i.e., the Normalized Relations. User Processing Requirements : The size and frequency of use of the DataBase, response time, security, backup, recovery etc. Characteristics of the DBMS and other components of the computer Operating environment. 
• Explain Components of Physical Database Design: Data Volume and Usage Analysis : To estimate the size or volume and the usage patterns of the database. Estimates of database size are used to select Physical storage devices and estimate the costs of storage. Estimates of usage paths or patterns are used to select the file organization and access methods, to plan for the use of indexes and to plan a strategy for data distribution. Data Distribution Strategy : Many organizations today have distributed computing networks. For these organizations, a significant problem in physical database design is deciding at which nodes (or sites) in the network to physically locate the data. Basic data Distribution Strategies are : Centralized : All data are located at a single site. It is fairly easy to do but it has at least three disadvantages : Data are not readily accessible at remote sites. Data communication costs may be high. The database system fails totally when the central system fails. Partitioned : The database is divided into partitions (fragments). Each partition is assigned to a particular site. Major advantage of this is that data is moved closer to local users and so is more accessable. Replicated : Full copy of database is assigned to more than one site in the network. This approach maximizes local access but creates update problems, since each database change must be reliably processed and synchronized at all of the sites. Hybrid : In this strategy, the database is partitioned into critical and non-critical fragments. Non-critical fragments are stored at only one site, while critical fragments are stored at multiple sites.
• Explain Database Implementation Phase: The builder or the database administrator normally requires a server computer which will be linked with hundreds and thousands of computer users who would want to share and interact with the server (database). For this purpose, the DBA might need the services of network administrators to connect the users with the server. The users are normally given the authorizations / permissions defined by their respective managers so that they can perform the authorized tasks while using the database facilities. In distributed computing environment, the database servers and users might be thousands of kilometers apart, so a lot of expensive telecommunication links are required to perform the designated tasks. NADRA and CRICKINFO are some of the typical examples of this type of databases.